internal parasites? treating in a planted tank

I think at least 4 of my 6 female Betta have internal parasites. All 4 are bloated (and have been for months as I thought they were just fat) and I noticed white, stringy poop from one of them. All are active and eating as normal. They are in a 40g breeder that never has nitrates above 10ppm. Water temp of 78, fully planted, tetras, Bolivian ram, and BN pleco as tank mates. I was looking for an anti parasitic food as I know most medications will kill live plants...but I can't seem to find one. Normally, they eat NLS small fish formula, ocean nutrition formula one flake, and a variety of frozen food. Both NLS and formula one have garlic. I don't have a quanantine tank :-( but can separate the female bettas in small containers to treat if necessary. Any ideas for a readily available anti parasitic food or plant friendly medication?